Project Summary Drug resistant cancers are an unfortunate global health problem that affects millions of families [6]. Inhibitors targeting cancers caused by mutations in the kinase domain of receptor tyrosine kinases often target the ATP binding site [7]. Although this method of treatment is generally very effective, mutations at the ?gate-keeper? position and residues farther away from the drug binding site not only cause weakened binding affinity for the drug, but can also increase kinase activity in the absence of drug. Addressing additional kinase activation is a major concern as undruggable cancers can easily continue to spread. My dissertation research aims to understand and quantify the effects these mutations have on kinase activation and thermodynamic stability using the kinase domain from the fibroblast growth factor receptor (FGFRs) family as a model system. Recently, we elucidated an allosteric network of residues in FGFR kinases spanning from the hinge region to the activation loop that are associated with activation. Using NMR relaxation experiments to provide residue specific information, I plan to quantify the effects of the gate-keeper mutant found in rhabdomysarcoma, and a hinge mutant, recently found to severely weaken inhibitor binding, on kinase dynamics. These dynamics will provide a clear picture of how these mutations hijack the kinase's allosteric network to increase activity and explain how hinge mutations far from the drug-binding site can confer resistance. Differential scanning calorimetry will also be employed to understand how drug resistant mutations affect the stability of the kinase in the apo and drug-bound form. Findings from this work will have major implications for future drug design to overcome these types of drug resistance mutations.